1. Field of the Invention
The present invention is generally concerned with wheel hubs having a built-in brake assembly, of the kind used, for example, in fitting out industrial vehicles, agricultural machinery, civil engineering plant and materials handling plant such as cranes and travelling overhead cranes.
2. Description of the Prior Art
Generally speaking, a wheel hub of this kind comprises a hollow body rotatably mounted on a fixed support sleeve, commonly referred to as a stub axle, having an external transverse flange to which a wheel may be attached by means of its rim flange. Within the hollow body is a brake assembly comprising at least one rotary disk adapted to be constrained to rotate with the corresponding wheel shaft. In practice, there are a plurality of rotary disks of this kind alternating with fixed disks.
The present invention is more particularly directed to the case where this brake assembly is disposed within an annulus.
This is the case, in particular, when the hollow body contains, in addition to a brake assembly of this kind, a gear assembly adapted to reduce the service speed of the hollow body to an acceptable value.
In this case, the gear assembly usually comprises a plurality of planet wheels operative between a sun shaft constrained to rotate with the wheel shaft and an annulus constrained to rotate with the stub axle, and the space within this ring is used to install the associated brake assembly.
As a corollary to this, within the hollow body, which forms a casing adapted to contain a fluid, there is accommodated a certain quantity of oil to lubricate the component parts of the gear assembly. In addition to lubricating the component parts of the gear assembly, this oil also cools the disks of the associated brake assembly.
This oil is inevitably subjected in service to centrifugal forces which apply it to the internal wall of the hollow body as an annular layer.
The brake assembly, disposed within the annulus, is necessarily spaced from the hollow body and may as a result be inadequately lubricated, lubrication being effective only below a certain rotation speed of the assembly.
This problem is accentuated by the fact that, at present, communication between the volume internal to the annulus and the external annular volume between it and the hollow body is relatively difficult, being obtained through the disks of the brake assembly, which form a chicane, and possibly, when the annulus is constrained by splines to rotate with the annulus carrier through which it is constrained to rotate with the stub axle, through these splines.
A general object of the present invention is to improve the conditions under which the brake assembly is cooled.